The present invention relates to a mechanism for driving a shaft in a linear fashion in response to a rotary input, and more particularly to such a mechanism in which the shaft is driven linearly by wire engaging drive rollers that are in turn positioned by retaining rollers.
A solution to the problem of conversion between rotary and linear motion in response to a rotary input is disclosed in U.S. Pat. No. 3,081,639 issued to Murray L. Hauptman, on Mar. 19, 1963 entitled "Feed Mechanism".
In the Hauptman device, a plurality of drive rollers are positioned about a shaft, each roller forming an acute angle with the longitudinal axis of the shaft. The rollers are driven by an outer race which rotates about the shaft and produces linear movement. The Hauptman device, however, is limited by the length of axial travel of the race. Restricting axial travel produces intolerable friction. Another problem associated with the Hauptman structure is that it is not readily adapted to use with small diameter shafts such as wires where only a small number of drive rollers can be employed.
The objects of the present invention are to overcome the above mentioned limitations of the Hauptman device and, at the same time, to provide an arrangement which reduces axial movement of the wire engaging rollers to a minimum without any frictional disadvantage.